The present invention relates generally to a biasing arrangement for use with a filter element. More particularly, the present invention relates to a filter element and a spring element forming an integral filter unit for use in a filtering apparatus.
In a known type of filtering apparatus, one or more elongated filter elements are arranged within a single housing often in a generally vertical orientation. The filter elements may be comprised of spun synthetic fibers, wound cotton, pleated paper or the like and are generally formed as a hollow cylindrical member. These hollow filter elements are arranged over fittings in a lower end of the housing which fittings communicate with a common collection chamber there below. An inlet opening is provided in the housing generally between the ends of the filter elements.
In order for a fluid to be filtered, the fluid must pass through the walls of the filter element. Accordingly, a sealing arrangement is preferably arranged at both upper and lower ends of each of the filter elements. In order to further ensure that the fluid does not bypass the filter elements, the fluid tightness of the seals are often further enhanced by the application of an axial compressive force on the filter elements. Accordingly, in the prior art a cover plate is often provided which is secured against the upper ends of the filter elements thereby urging the lower ends of the filter elements into tight engagement about the fittings.
Due to variations in height of both the filter elements themselves and the various housings with which the filter elements may be used, it has been found desirable to employ a biasing arrangement between the cover plate and the upper end of each of the filter elements. In this way, compensation for the variations in height is accomplished while still maintaining appropriate seals at the upper and lower ends of the filter element.
In prior art systems, a metallic spring element has often been used. The spring element may include a cup-like metal disk arranged at an end of the spring element which disk is adapted to abut the upper end of a respective filter element. Also, a centering pin adapted to be received within the longitudinal bore of the filter element is often provided to aid in retaining the spring element in place.
Numerous disadvantages occur during the use of such a metallic spring element and disk. Firstly, it is sometimes difficult to maintain each of the spring elements on the end of the respective filter elements while attempting to secure the cover plate over the plurality of filter elements. If one spring element becomes dislodged during assembly, it is necessary to remove the cover plate and realign the disk and spring before attempting to fasten the cover plate securely to the housing. Additionally, it is not always apparent that a spring element has been dislodged. Therefore, a housing may be operated with fluid bypassing one or more filter elements. Also, a dislodged spring element can be difficult and time consuming to retrieve from the bottom of a vertical housing. A further disadvantage occurs when the filter elements are spent and must be changed. In addition to handling a plurality of filter elements, time is required for collecting the spring elements, holding them, and replacing the spring elements on fresh filter elements. Also, spring elements may be lost or misplaced during changing of the filter elements. Still further, the compatibility of the metal spring with the fluid must be considered. In other words, chemicals contained in certain fluids may cause an adverse effect on the composition of the metallic spring thereby causing corrosion of the spring and/or contamination of the effluent. Still a further disadvantage of the known system is the relatively high cost of the metal spring and seal disk arrangements.
One proposed solution includes the use of a rubber doughnut or sealing ring attached to the lower end of the filter element. The doughnut was purported to provide both sealing and centering of the lower end of the filter along with the resilient function of a spring. A plug of suitable material was also proposed for the upper end of the filter element. Such an arrangement was found not to be entirely satisfactory. The cost of separate doughnuts and upper end plugs was higher than anticipated and the time required for handling of the extra elements may be unacceptable.
Accordingly, it is an object of the present invention to overcome the disadvantages mentioned above in the prior art biasing arrangements for filter elements within a filtering apparatus.
It is a further object of the present invention to provide a biasing arrangement for use with a filter element which is both inexpensive to produce and relatively easy to handle during assembly.
Still a further object of the present invention is to provide a biasing arrangement which is readily disposable when the filter element has become unusable. Yet a further object of the present invention is to provide a biasing arrangement which is more readily compatible with the fluid stream passing through the filter element.
Additionally, it is an object of the present invention to provide a filter unit for use in a filtering apparatus which can be readily installed by a simple and expeditious procedure in housings having slight variations in overall height.
These objects and others are achieved by a biasing arrangement according to the present invention for use with a filter element having a longitudinal bore therethrough. The biasing arrangement includes a spring element having first and second ends and comprised of a plastic material. The spring element is deformable by pressure applied in a direction generally along an axis extending between the first and second ends. A sealing disk adapted to seal an end of the longitudinal bore of the filter element is also comprised of a plastic material. The sealing disk is positively secured to an end of the spring element.
The sealing disk may be secured to the end of the spring element by spin welding, fusion welding, hot melt welding, ultrasonic welding or another suitable adhesive method. Alternatively, the spring element and the sealing disk may be molded as a single unit. In a preferred embodiment, the spring element and the sealing disk are comprised of a compatible plastic material. In an especially preferred embodiment, the plastic material of the spring and the sealing disk is polypropylene.
In accordance with a further aspect of the present invention, a filter unit is provided for use in a filtering apparatus including at least one filter unit. The filter unit includes an elongated filter element having a longitudinal bore therethrough. A spring element having first and second ends is deformable by a pressure applied in a direction generally along an axis extending between the first and second ends. A sealing disk for sealing an end of the longitudinal bore of the filter element is also provided. The spring element, the sealing disk and the filter element are positively secured to one another to define an integral unit.
Further, in the preferred embodiment, the spring element has a nonlinear load deflection characteristic. In particular, the spring element develops a large force during initial deformation followed by a substantially constant force upon further longitudinal deflection of the spring element.